Gloss is a surface attribute causing a shiny or lustrous appearance. It is generally associated with specular reflection by the object. However, specular reflection can vary from one surface to another as follows:
1. The fraction of light reflected in the specular direction.
2. The manner and extent to which light is spread to either side of this specular direction.
3. The change of fractional reflectance as specular angle changes.
There are at least six different visual criteria by which glossiness is ranked (Table 1).